College

115 mL of a gas is at 45.8 kPa and [tex]$57.2^{\circ} C$[/tex]. What is the volume of the gas at 99.3 kPa and [tex]$12.3^{\circ} C$[/tex]?

Answer :

To find the volume of a gas when it undergoes changes in pressure and temperature, we can use the Combined Gas Law. This law combines Boyle's Law, Charles's Law, and Gay-Lussac's Law. It relates the pressure (P), volume (V), and temperature (T) of a gas in two different states.

The formula for the Combined Gas Law is:

[tex]\[
\frac{P_1 \times V_1}{T_1} = \frac{P_2 \times V_2}{T_2}
\][/tex]

Where:
- [tex]\(P_1\)[/tex], [tex]\(V_1\)[/tex], and [tex]\(T_1\)[/tex] are the initial pressure, volume, and temperature.
- [tex]\(P_2\)[/tex], [tex]\(V_2\)[/tex], and [tex]\(T_2\)[/tex] are the final pressure, volume, and temperature.

Given:
- Initial volume, [tex]\(V_1 = 115 \, \text{mL}\)[/tex]
- Initial pressure, [tex]\(P_1 = 45.8 \, \text{kPa}\)[/tex]
- Initial temperature, [tex]\(T_1 = 57.2^\circ \text{C}\)[/tex]
- Final pressure, [tex]\(P_2 = 99.3 \, \text{kPa}\)[/tex]
- Final temperature, [tex]\(T_2 = 12.3^\circ \text{C}\)[/tex]

Step 1: Convert the temperatures from Celsius to Kelvin.

To convert from Celsius to Kelvin, use the formula:

[tex]\[ T(\text{K}) = T(\text{C}) + 273.15 \][/tex]

So,
- [tex]\(T_1 = 57.2 + 273.15 = 330.35 \, \text{K}\)[/tex]
- [tex]\(T_2 = 12.3 + 273.15 = 285.45 \, \text{K}\)[/tex]

Step 2: Use the Combined Gas Law to solve for the final volume, [tex]\(V_2\)[/tex].

Rearrange the formula to solve for [tex]\(V_2\)[/tex]:

[tex]\[
V_2 = \frac{P_1 \times V_1 \times T_2}{P_2 \times T_1}
\][/tex]

Plug in the values:

[tex]\[
V_2 = \frac{45.8 \times 115 \times 285.45}{99.3 \times 330.35}
\][/tex]

Simplify and calculate:

[tex]\[
V_2 \approx 45.83 \, \text{mL}
\][/tex]

So, the volume of the gas at a pressure of 99.3 kPa and a temperature of [tex]\(12.3^\circ \text{C}\)[/tex] is approximately 45.83 mL.